Osteoporosis is a common disease associated with low bone mineral density (BMD). Bone is lost naturally with age, and this tends to be accelerated after menopause. People with low bone density often do not realize they are at risk of osteoporosis until a fracture occurs, by which stage bone may have been irreplaceably lost from the skeleton. There are a number or risk factors for osteoporosis, but the most important is thought to be low BMD. Early recognition of bone loss is important in the identification of individuals at risk of osteoporosis, particularly in view of the increasing availability of preventative and therapeutic interventions that can reduce the impact of bone loss and prevent the increase of fracture risk due to bones becoming more fragile.
Until recently, bone mineral density was measured mainly through the use of x-ray based technologies such as dual energy x-ray absorptiometry (DXA or DEXA) and, to a lesser extent, quantitative computed tomography (QCT). Other techniques were used earlier, such as single photon absorptiometry, but are no longer widely used. DXA and QCT techniques have many desirable characteristics, such as high sensitivity and the ability to accurately predict fracture risk, but use ionizing radiation and relatively expensive equipment. More recently, ultrasound has become available for bone assessment. Using quantitative ultrasound (QUS), it is possible to measure or estimate ultrasonic characteristics of bone and thereby estimate bone mineral density and assess the risk of fracture. Ultrasound also has been shown to be reliable in estimating bone mineral density and predicting the risk of fracture, and has the desirable characteristics of not involving ionizing radiation and using lower cost equipment. In addition, there is a class of x-ray based medical devices called small C-arm fluoroscopes, or simply small C-arms, that typically are used for both surgery and diagnosis of extremities, but can be provided with the additional capability of making bone assessment measurements.
As an example of commercially available products of this type, Hologic, Inc. of Bedford, Mass. offers a line of DXA equipment under the trade names ACCLAIM and QDR and model designations such as 4500 and 1000, an ultrasound bone sonometer under the trade name Sahara, and a small C-arm under the trade name Fluoroscan followed by model designations. See, e.g., U.S. Pat. No. 5,778,045 pertaining to x-ray bone densitometry, U.S. Pat. Nos. 5,755,228 and 5,785,041 and U.S. patent application Ser. No. 08/477,580 pertaining to ultrasound bone sonometry, and U.S. patent application Ser. No. 08/794,615 pertaining to small C-arm x-ray devices. See, also, a brochure entitled "SAHARA Clinical Bone Sonometer" printed for Hologic, Inc. Under the designation B-130 U.S. (10/97). Said patents and applications and said brochure are hereby incorporated by reference in this patent specification as though fully set forth herein.
In non-analogous fields of technology and business, consumers have long used cards such as credit and debit cards and smart cards to pay for goods and services, and individuals have used access cards to gain admittance to controlled facilities. While often the purchaser hands the card over to a sales person who inserts it in a card reader, there are cases in which the purchaser has direct access to the card reader, e.g., at some gas stations.
However, patients typically do not operate bone sonometry or densitometry or small C-arm equipment, and no patient-provided cards are known to be involved in turning such diagnostic equipment on to carry out some, but perhaps not all, of the procedures such equipment carries out. Nor are the owners or operators of bone sonometers or densitometers known to be required to use cards to make the equipment carry out examinations. Indeed, charging a card to turn on a bone sonometer or densitometer for an examination may not appear practical at first blush, and may be counter-intuitive, because some procedures do not directly produce revenue to the owner or operator. For example, a bone sonometer or densitometer may require periodic calibration examinations, e.g., once a day, in which the equipment measures a calibration object (phantom) rather than a patient or makes a measurement through a medium other than a patient's body or extremity. Quality control procedures and service and maintenance procedures can also be similar or even identical to patient examinations from the machine's point of view, but also are not directly revenue-generating for the machine's user. Similar, though not necessarily identical, considerations can apply to DXA bone densitometers and small C-arm equipment.